1. Field of the Invention
This invention relates to a receiving apparatus for receiving television broadcast signals of a so-called chargeable broadcasting system, and a recording method.
2. Description of the Prior Art
The conventional chargeable broadcasting system for e.g. television broadcasting is a system in which viewers desire to view particular broadcasting and conclude a fee-paying reception contract with the broadcasting company to receive broadcasting services and is called a pay service, pay television or limited reception system.
In a broadcasting system over a cable, such as a cable television system (CATV), belonging to the chargeable broadcasting system, reception can be controlled by cable connection. However, on radio or cable-less broadcasting, the same electric waves also arrive at a non-subscriber. For this reason, broadcast signals are scrambled so that the program may not be viewed by non-subscribers. Besides, if a particular program is charged in CATV by a particular charging system, means for scrambling signals is similarly required. If the signals are scrambled in this manner, the contracting subscribers receive regular program signals using a decoder.
The above-mentioned chargeable broadcasting is put to practical use by e.g. a pay cable for a cable system and by e.g. a subscription television (STV) for a surface radio system. Broadcasting by a direct broadcasting satellite is under investigation. When the program supplying company distributes head-end CATV programs of a number of territories by communication satellites, scrambling is introduced for preventing reception by non-subscribers.
It is noted that signal scrambling is frequently controlled by pseudo random (PN) signal series (scrambling signal series) for elevating safety. The receiving side descrambles the scrambled signals using the same signal series (in this case, descrambling series) for reproducing the original signals. Scramble keys are sent to the receiving side for generating the PN signal series.
Besides, it is necessary with the chargeable broadcasting system to control descrambling based on the contents of the contract of the respective subscribers, such as services, contract terms or prepaid amounts. The information required for this purpose is also transmitted to the receiver.
The information for controlling scramble keys or chargeable broadcasting is termed the pertinent information. The media used for transmission of the pertinent information include physical media such as a wireless medium by electric waves, a magnetic card or IC card, and cable media such as telephone lines. These media are different in their characteristics, such as rates of transmission, volume of information, reliability in transmission and bidirectivity.
Transmission of personal information to each receiver by electric waves is generally termed addressing by electric waves. When the personal information is transmitted by electric waves, high transmission reliability is of utmost importance because scrambled broadcasting signals cannot be descrambled unless the pertinent information is received, and some information is direct monetary information.
It is noted that the pertinent information in the current television scrambling transmission system may be typified by, for example, program information containing the information concerning the program and the scramble key, control information for instructing forced on/off of the descrambling function of the decoder, personal information having a work key for decoding the contract information and the common information (i.e. both the program information and the control information) for each subscriber and message information for additionally displaying the information concerning the chargeable broadcasting services at the receiving side. It is noted that the personal information is coded by a master key allocated to each subscriber when the information is distributed by electric waves. The pertinent information is transmitted by electric waves by packet transformation over data channels.
The pertinent information in the scrambling transmission system for high definition television system is the information similar to the above-mentioned current television scrambling transmission system and is transmitted by electric waves by packet transmission over data channels.
Meanwhile, if the usual receiver for chargeable broadcasting is combined with e.g. a video tape recorder or a cassette tape recorder and the chargeable broadcasting is to be recorded by these recorders, the recorders record the signals no matter whether the signals, which are in the scrambled state, may be descrambled or not.
If the signals are recorded in the non-descrambled state, and reproduced subsequently, the signals recorded on the video tape recorder become striped patterns with no sound reproduction, while those recorded on the cassette tape recorders become silent signals. In other words, the program has not been recorded on the tape.
Above all, in the case of appointment recording using a timer or take-care recording for absence, recording is not made with the user actually checking the state or contents of recording. On the other hand, when setting the appointment recording or take-care recording for absence, it may occur that the program channel or broadcasting time and, in the case of satellite broadcasting, the particular satellite (if there are plural satellites) or the scrambling contract conditions, may be set in a mistaken manner by the user.
In such case, there is a risk that, even if the user feels that recording has been made as he set, recording is actually not made. Such risk is particularly high when only a certain program becomes chargeable in accordance with a pay-per program contract.